Stringed Nano Beads Could Improve Lifespan of Lithium-Ion Batteries

Researchers continue their work to improve lithium-ion battery design with the latest hope for a longer lifespan found in silicon nanotechnology developed at the University of Maryland.

A team in the university’s Nanocenter that included YuHuang Wang, an assistant professor in the department of chemistry and biochemistry, has created nanoscale beads of silicon, about 10,000 times thinner than a piece of paper, that could extend the number of charging cycles lithium-ion batteries can go through by about 10 times the current design. This potentially could allow electric vehicles to travel farther on a single charge, as well as have applications for mobile phones, cameras, and other devices that use lithium-ion batteries.

Graphite is typically the electrode used in current lithium-ion battery design, but silicon is actually a better material, storing up to 10 times more lithium ions than graphite. However, silicon has been tricky to work with because it tends to crack and break with overuse, though researchers have been working for some time to solve this problem.

Tiny beads of silicon, grown on a tube 10,000 times thinner than a piece of paper, could store up to 10 times more lithium than graphite, a component of many commercial batteries. A team in the university’s Nanocenter that included YuHuang Wang, an assistant professor in the Department of Chemistry and Biochemistry, have created the beads using a molecule found in food flavorings and a gas containing silicon. (Source: University of Maryland Nanocenter)

The work is reminiscent of similar research being done at the University of Southern California under the tutelage of Chongwu Zhou, professor at the USC Viterbi School of Engineering. Researchers there replaced the graphite anodes that are typically used in the batteries with silicon nanowires with pores that allow the silicon to expand and contract without breaking.

Wang and his team took a slightly different approach, but the concept for how the silicon holds together well under the charging and discharging process is quite similar. The University of Maryland researchers, which also included mechanical and materials engineering scientists, grew beads of silicon on a carbon tube less than 50 nanometers wide. They accomplished this by attaching part of a molecule sometimes found in food flavorings along the tube and then flooding it with a gas containing silicon.

Researchers then charged the silicon with lithium ions, creating a more resilient structure for the silicon because the beads are more flexible than a typical flat silicon coating, they said. This resiliency is in part thanks to the organic molecule used to attract the silicon to the tube, which allowed it to bond more strongly and is thus less likely to break during the electrochemical process.

“As the nanobeads of silicon were charged by the lithium, they grew and shrank without cracking or ripping,” Wang said in a news release on the university’s website.

Researchers published an article about their development in the journal
ACS Nano, as well as posted a video online of the
beads in action under an electron microscope.

Definitely true, Liz. I've been writing about this subject since 1988, and the realities have never once matched the promises during that time. Last year, I talked with a battery expert who designed GM's first electric car batteries in the 1970s and also designed fuel cells for NASA's Gemini program in the '60s. I asked him why it's so difficult. His answer: "Each new idea looks really good until you discover all the problems." He believes that developing a new battery chemistry typically takes 20-30 years.

In covering all this research, I can see how true that is, Chuck. I never thought it would be so complicated to improve something we all take so granted and that has been with us for so long, but it seems far more difficult than the average person would imagine. There seems to be a real effort in this area, though, and different research teams working on similar methods to improve batteries...perhaps the competitive spirit will drive them to faster improvements.

Nice story, Liz. This is why research is so critical to the development of battery technology. Improving batteries is (in some ways) similar to curing cancer: It isn't going to happen without some serious research in our universities and national labs.

Sorry if you feel it's not clear, William, but thanks for reading anyway. Maybe a link to what the university has to say about the technology may help? http://www.nanocenter.umd.edu/news/news_story.php?id=7147

Thanks Elizabeth. The only interpretation that made sense to me after reading the full article is that this development made the lifespan better than previous SILICON cathode Li batteries, not the currently used graphite type. So I think the real improvement is the energy density, not the lifespan compared to current batteries. Still, 10x the energy is a major breakthrough.

In my understanding, Tcrook, it is the lifespan (the number of charging cycles) but I think other research has been able to increase energy density as well. Here is the link to the release about this news so perhaps that could tell you more: http://www.nanocenter.umd.edu/news/news_story.php?id=7147

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